The two float chambers are at different heights. Two different float levels, two different fuel levels. So how does that work?
Paul
I believe they are in series, not parallel. The float nearest the carb being the last in line, so it would set the fuel height in the carb. The forward float is acting as a reservoir, it only has to drain completely into the rear bowl that sets the height. That is probably why the forward float is much higher. This is just a guess.
I would note that when Alp turns on the Nitro in top gear on his bike the fuel bypasses the float bowl and enters the carb directly. This is because the float would slow the delivery of the fuel down considerably. At wide-open throttle in top gear, the engine pulls in all the fuel it demands (thus ignoring the fuel height). He does not want the float slowing down the fuel delivery.
David